Bad news, everyone. The melting of ice sheets in Greenland and Antarctica is on track to meet the United Nation's "worst-case scenario" forecasts, threatening millions of people worldwide with severe flooding each year.
In the damning study published in the journal Nature Climate Change, researchers from the University of Leeds in the UK and the Danish Meteorological Institute found that melting from Antarctica has pushed global sea levels up by 7.2 millimeters since the ice sheets were first monitored by satellite in the 1990s, while Greenland has contributed another 10.6 millimeters. On top of these glacial giants, there are also many smaller glaciers around the world that are also melting and fuelling sea level rise.
Altogether, the world's oceans are now rising by 4 millimeters each year as a result of thawing ice sheets. If melting continues to increase at this rate, the ice sheets could raise sea levels by a further 17 centimeters by the end of the century, exposing a further 16 million people to annual coastal flooding and destruction.
This, say the researchers, is almost exactly the "worst-case scenario" put forward in the United Nations Intergovernmental Panel on Climate Change (IPCC).
"If ice sheet losses continue to track our worst-case climate warming scenarios we should expect an additional 17 centimeters of sea-level rise from the ice sheets alone. That's enough to double the frequency of storm-surge flooding in many of the world's largest coastal cities,” Dr Anna Hogg, study co-author and climate researcher in the School of Earth and Environment at Leeds, said in a statement.
There are a number of reasons why the projections appear to have underestimated sea level rise, according to the researchers. For one, the existing models do not take into account clouds and cloud-formation, which help to modulate surface melting. Equally, many ignore short-term weather events, which are also likely to change in the face of further longer-term climate change.
This has some big implications for the way the world plans to tackle climate change and the effects it will take have on our planet. The IPCC is an attempt to provide the world with scientific information about the risks of human-induced climate change and the way it will affect both the natural world and the human world. If we’re are already inline with its worst-case scenarios of sea-level rise, this means our guidebook to avoid a full-blown climate crisis might need revising.
"Although we anticipated the ice sheets would lose increasing amounts of ice in response to the warming of the oceans and atmosphere, the rate at which they are melting has accelerated faster than we could have imagined," explained Dr Tom Slater, lead author of the study and climate researcher at the Centre for Polar Observation and Modelling at the University of Leeds.
"The melting is overtaking the climate models we use to guide us, and we are in danger of being unprepared for the risks posed by sea level rise."